Purdue University Graduate School

Verhagen Thesis.pdf

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posted on 2022-10-17, 19:17 authored by Garrett S VerhagenGarrett S Verhagen

Few contemporary studies have examined nutrient accumulation and partitioning of modern corn (Zea mays L.) hybrids grown under in-season sulfur (S) and potassium (K) nutrient management. A fertilizer x hybrid field experiment was conducted during the 2020 and 2021 growing seasons in West Lafayette, Indiana to (1) determine the efficacy of in-season fertilizer management as a strategy to increase grain yield among different modern hybrids, (2) determine the extent to which nutrient harvest index (NutHI) relates to other plant traits under intensive agronomic management, and (3) determine whether grain yield and within-plant nutrient dynamics respond to in-season S and K management differently depending on hybrid. The three fertilizer treatments (whole plot) were (1) Control, no S or K applied, (2) Sulfur, 22.4 kg S ha-1 broadcast applied as ammonium thiosulfate (ATS) [12-0-0-26S] immediately after planting, and (3) Sulfur_Potassium, S (from treatment 2) plus 108 kg K ha -1 topdress applied via Aspire™ [0-0- 58(K2O)-0.5B] at the V4 growth stage. The experiment consisted of four modern Pioneer® corn hybrids (subplot) that varied in crop relative maturity (CRM) from 105 to 114 days planted at the same density following fall strip tillage in a continuous corn production environment. Aboveground dry matter accumulation (DM) and plant tissue concentrations of N, P, K, S, and B were measured via whole-plant samples at V6, R1, and R6. Soil K levels were above the critical K level prior to K application but soil S was not reliably determined. 

Grain yields following Sulfur and Sulfur_Potassium treatments were similar, averaging 14.6 Mg ha-1 , which represented a 20% increase over the 12.2 Mg ha-1 observed in the Control. Grain yield gains following S application were the result of increased S uptake, first detected at V6, which alleviated S-deficiency and improved the N to S ratio (N:S) within the plant. K application did not affect grain yield. The greatest contrast in grain yield among hybrids corresponded to extremes in CRM, from 12.9 Mg ha-1 in 105_day to 14.5 Mg ha-1 in 114_day. Fertilizer x hybrid interactions were rarely observed among measured variables with the notable exception of HI, which was increased in later maturity hybrids (111_day and 114_day) by Sulfur and Sulfur_Potassium relative to Control, but was unaffected by fertilizer treatments in 105_day and 110_day hybrids. Most phenotypic parameters were positively influenced by Sulfur and Sulfur_Potassium relative to Control, including above-ground dry matter accumulation (DM), nutrient accumulation, dry matter harvest index (HI), nutrient harvest index (NutHI), and 13 grain/stover nutrient concentrations at maturity. Compared to Control, total plant DM was increased following Sulfur and Sulfur_Potassium by an average of 14% at V6, 16% at R1, and 20% at R6. Whole-plant biomass totals were similar between Sulfur and Sulfur_Potassium, averaging 693 kg DM ha-1 at V6, 10909 kg DM ha-1 at R1, and 26170 kg DM ha-1 at R6; however, K application increased the proportion of total DM partitioned to stover rather than grain, which reduced HI from 0.58 under Sulfur to 0.56 under Sulfur_Potassium. 

Nutrient accumulation (of N, P, K, S, and B) was influenced by in-season S and K application at all growth stages relative to the Control. Sulfur application increased V6 wholeplant S and K concentrations, but lowered P and B concentrations. Applying in-season K boosted V6 N and P concentrations, but temporarily reduced K uptake by 10%. Due to gains from S and K application in both DM and nutrient concentration at maturity, total nutrient accumulation in Sulfur_Potassium increased by up to 25% in N, 28% in P, 59% in K, 77% in S, and 44% in B. Total plant DM at maturity was reduced by 14% in the low-yielding 105_day hybrid relative to other hybrids at maturity, leading to similar reductions in nutrient accumulation despite relatively high nutrient concentrations. There was little hybrid variation in whole-plant P, S, and B uptake but substantial hybrid variation in N (9%) and K (21%) uptake. Partitioning of N, P, and K between stover and grain at maturity was influenced by the increased grain nutrient concentrations following Sulfur_Potassium relative to Sulfur. Grain nutrient concentrations under Sulfur relative to Sulfur_Potassium increased from 1.19% N to 1.24% for N, from 0.32 to 0.36% for P, and from 0.39 to 0.44% for K. When Sulfur_Potassium increased grain P and K concentrations over Sulfur, grain nutrient content (i.e., removal) also increased even when grain DM was similar, boosting removal from 48 kg P ha-1 to 54 kg P ha-1 , and from 58 kg K ha-1 to 65 kg K ha-1 . In contrast, grain S and B concentrations, at 0.08% S and 3.3 ppm B, as well as grain contents, at 12.4 kg S ha-1 and 0.05 kg B ha-1 , were similar under both Sulfur and Sulfur_Potassium. As previously stated, NutHI increased substantially in response to both S treatments relative to the Control. The NHI in the Control was just 0.57 versus 0.65 under S treatments while the P harvest index (PHI) was 0.71 versus 0.84, S harvest index (SHI) was 0.50 versus 0.57, and B harvest index (BHI) was 0.35 versus 0.39. Hybrid differences in NutHI were relatively small and were related to both DM and nutrient concentrations at maturity. 

While further research is necessary to accurately assess nutrient accumulation and partitioning trends as nutrient management strategies continue to evolve, this study demonstrated 14 that in-season S applications can effectively increase grain yield under S-limiting conditions. Inseason K application did not increase grain yield over Sulfur alone (presumably due to adequate soil K); however, added K still enhanced both grain nutrient removal and NutHI. Furthermore, the influence of plant nutrient concentrations at maturity in both grain (positive) and stover (negative), on NutHI was strongest under fertilizer treatments and NutHI was less dependent on grain yield, total DM, or HI trends. Under hybrid treatments, the influence of nutrient concentrations on NutHI was dependent on DM parameters. While grain yield, DM, and HI were likely to have been contributing factors in NutHI determination, stover nutrient concentration was the most consistent factor related to NutHI across fertilizer and hybrid treatments. The observed variation in NutHI might imply there is still potential for improvement of this index beyond HI alone. Although fertilizer and hybrid treatment responses in whole-plant nutrient concentration were strong during the vegetative period, they were less indicative of NutHI than those at maturity. The positive impact of Sulfur_Potassium on grain nutrient concentration, in the absence of a grain yield response, highlighted a potential disparity between achievable levels of grain nutrient concentration and yield. While in-season nutrient applications can substantially increase grain yields, our results show that in-season fertilizer can also affect nutrient accumulation and partitioning, which are key factors to be considered when making nutrient management decisions. 


Degree Type

  • Master of Science


  • Agronomy

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Tony Vyn

Additional Committee Member 2

Cankui Zhang

Additional Committee Member 3

Mary S Gumz

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